If a battery is too low to charge, some hobbyists "jump" it from a charged battery. While effective, this bypasses safety protocols and should only be done with extreme caution and constant voltage monitoring. Summary Table for Quick Reference Importance B+ 20V Positive Output Main Power T Temperature (Thermistor) Safety / Charging C / D Battery ID & Health B- Ground / Negative Main Power
Here are the raw multimeter readings from a teardown of a Hart battery, using the negative terminal as a reference point. These readings give you a concrete understanding of the electrical relationships between pins [7†L29-L33].
This is a safety pin. It connects to an internal NTC thermistor that monitors the temperature of the Lithium-Ion cells. If the battery gets too hot during use or charging, the tool or charger will cut power to prevent a fire or cell damage. hart 20v battery pinout diagram better
The Hart 20V battery pinout diagram consists of several pins, each with a specific function. The following is a breakdown of the pinout diagram:
This pin connects to an internal NTC thermistor. It tells the charger and the tool how hot the battery is. If the resistance on this pin indicates the battery is too hot (or too cold), the tool will cut power to prevent a fire or permanent cell damage. 4. C-Terminal (Communication / Identification) Location: The remaining inner pin(s). If a battery is too low to charge,
The standard external connector on the battery pack includes the following primary pins: Positive (+)
A temperature monitoring pin that connects to an internal NTC thermistor. This pin allows the charger and tool to detect if the battery is overheating or too cold to operate. These readings give you a concrete understanding of
: If your tool shuts off suddenly and the battery feels hot, the TH circuit has triggered a high-temperature lock. Allow the pack to cool completely before placing it back onto a charger.
Delivers the full voltage of the battery pack (nominally 18V, peaking at 20V when fully charged). 2. Negative Terminal (-) Location: The outermost slot on the opposite side. Function: The common ground for the circuit. 3. T-Terminal (Thermistor / Temperature) Location: One of the inner pins.
A standard Hart 20V lithium-ion battery typically features a 4-terminal or 5-terminal interface on its connector slot. When looking directly at the battery terminal slot with the latches facing up, the pins generally follow this layout from left to right:
Safety and protection circuits Hart batteries include protection circuitry: over-current cutouts, over/under-voltage protection, and temperature monitoring. The connector pins may be routed through the battery management system (BMS) so directly shorting pins or bypassing the BMS risks damage, fire, or injury. Always discharge and isolate properly before probing, and avoid shorting B+ to B−.